International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 11 Issue: 09 | Sep 2024
p-ISSN: 2395-0072
www.irjet.net
Caster Angle and KPI Variation through Worst Case & RSS Method Ravindra Kachare1 Mohan Patwari2 1Team Lead, Tata Technologies, ERC, Chassis, Tata Motors, Pune Maharashtra, India 2Tech Lead, Tata Technologies, ERC, Chassis, Tata Motors, Pune Maharashtra, India
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Abstract - Caster angle is one of the main parameters of suspension system which has significant impact on a vehicle’s handling at time of cornering, straight-line stability and high speed stability. Caster angle is a slope created by an imaginary line passes from upper ball joint to the lower ball joint i.e. KPI (king pin inclination) to center line of tyre when seen from side of vehicle. Caster angle is said to be positive if strut top point in MacPherson suspension is inclined towards rear side of vehicle or KPI line inclined towards vehicle rearward. Caster angle is said to be negative if KPI inclined towards vehicle front which creates angle with center line of front tyre. Positive and negative caster angle set in vehicle depending upon the suspension system geometry requirement and overall vehicle performance. Caster value varies if strut top point and lower ball joint contributor parts are not in specified tolerance limit which changes the king pin inclination. To check maximum or minimum caster variation as per the tolerance given in part like control arm, chassis, wheel end, strut etc., a tolerance stackup analysis is performed which helps to get maximum and minimum caster value. Caster angles are generally used to improve vehicle’s steering balance at time of high speed and cornering. Positive caster increases steering effort also the amount of caster set into vehicle’s suspension system is a balance between stability and steering effort.[5]. Key Words: Tolerance stackup analysis for caster angle and KPI variation.
1.INTRODUCTION In field of automobile engineering, suspension plays an important role in terms of ride comfort, cornering etc. To maintain all the vehicle performance, all the suspension parameter to be designed in such a way that it maintain its quality like design, drafting, manufacturing and inspection. Suspension design is very complex structure which is the combination of both kinematics as well as it should also bear all road load. The kinematics of suspension includes many suspension real time travel and turn via rack and pinion. Kinematics plays a major role in suspension desired application besides the kinematics suspension system should bear the road load condition which includes 1G, 2G, 3G, load which generates through articulation, cornering and weight shift while braking and accelerating. This complex suspension design requires an inspection of all components to be 100% defect free. Suspension components should be defect free from design, CAE, manufacturing. This topic focuses mainly on the component and assembly level tolerances. Defining tolerances is the good practise before part manufacturing. Here, tolerance are the most common parameter that are available and to be given in the drawing as per the best practises of designer but how the tolerance of component will affect the tolerance of assembly? The purpose of providing tolerance is to ensure functionality, improves communication between designer and manufacturer. The tolerances in the drawing are to be defined in such a way that the suspension parameter such as caster angle nominal values remains into the specified tolerance zone, Ideally the caster angle in passenger vehicle are kept as 3 to 5 degree which varies as per change in vehicle weight at front axial and rear axial. In this exercise all the tolerance are defined with following ASME Y14.5 standard, While designing the kinematics, testing road load and providing tolerance in the drawing, the tolerance stackup are need to be performed. The tolerance stackup is proven method to resolve the upcoming issues to allow the application of any assembly. It also includes the process of assembling the assembly to make suspension work.
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